Machine frame, having a biased wire girdle, and a method for biasing such a girdle

ABSTRACT

A frame for a heavy machine, especially a press, is surrounded by a transverse girdle comprising a great number of turns of a steel wire or the like. The wire is biased under tension whereby the girdle exerts an inwardly directed force holding the frame under compression in its unloaded condition. The girdle is mounted on the frame before the wire has been biased and the biasing is effected by expansion of the girdle. The expansion is carried out by means acting between the frame and the girdle which eliminates the need for expanding the frame by displacing a portion thereof relatively to the remainder of the frame.

Unite States atent Jonsson 1451 May 20, 1975 MACHINE FRAME, HAVING A BIASED Finn Lennart Jonsson, Ystad, Sweden Assignee: AB Carbox, Ystad, Sweden Filed: Jan. 9, 1974 Appl. No.: 431,874

Inventor:

[30] Foreign Application Priority Data Jan. 19, 1973 Sweden 7300775 References Cited UNITED STATES PATENTS 10/1965 Hassellof 100/214 X 3,800,695 4/1974 Jonsson et a1. 100/214 Primary ExaminerBilly J. Wilhite Attorney, Agent, or FirmFlynn & Frishauf [57] ABSTRACT A frame for a heavy machine, especially a press, is surrounded by a transverse girdle comprising a great number of turns of a steel wire or the like. The wire is biased under tension whereby the girdle exerts an inwardly directed force holding the frame under compression in its unloaded condition. The girdle is mounted on the frame before the wire has been biased and the biasing is effected by expansion of the girdle. The expansion is carried out by means acting between the frame and the girdle which eliminates the need for expanding the frame by displacing a portion thereof relatively to the remainder of the frame.

8 Claims, 5 Drawing Figures PAIENIEU HAYZUIQYS 3,884 142 SHEET 2 or 3 MACHINE FRAME, HAVING A BIASED WIRE GIRDLE, AND A METHOD FOR BIASING SUCH A GIRDLE The present invention relates to heavy machines, such as presses and especially gap presses, comprising a frame provided with a tension-biased wire girdle.

In the operation of a heavy duty machine the frame thereof is subjected to outwardly directed reactional forces tending to deform the frame and, in serious cases, resulting in a permanent deformation or rupture. In order to counteract such phenomena it is known to surround the frame with a wire winding girdle as set out above. The pre-stressing of the wires is normally selected so that the inwardly directed force resulting therefrom is greater than the reactional forces also at maximum load on the frame or, stated in other words, also when the frame is subjected to a maximum load, at least in the portions thereof directly surrounded by the girdle, the net stress on its material should be compression rather than tension. In this way it is achieved that no outwardly directed forces which might result in deformation of the frame can arise at least not in the parts of the frame which are adjacent to the girdle.

When a machine manufacturer is to equip this machine with such a girdle he can choose between two different methods. According to one of those methods the first step is to mount the holder, or bobbin, on the frame and then to apply the wire winding onto the bob bin during which procedure the wire is, under tension bias, delivered from a stationary spool. This requires that all, or in any case the major part. of the machine frame participates in the rotational movement of the bobbin. For that purpose the frame is generally placed on the working table of a big vertical turning lathe. It is, however, easily understood that the transport of such a heavy and big workpiece to a vertical lathe is a difficult and expensive work and also that corresponding difficulties are connected to the requirement for an accurate centering of the workpiece on top of the table of the lathe. A further disadvantage is that the bearings of the lathe are subjected to heavy loads. Still another problem arises when, which is often the case, the winding bobbin is not circular but e.g. oval. In order for the biasing force in the wire then to be kept constant it is accordingly necessary either continuously to vary the rotational speed of the workpiece or to resort to compensating measures at the wire delivery apparatus.

The above comments apply to machine frames which are big and heavy but not of excessive weight. However, in several technical fields there is a definite trend towards the use of bigger and heavier machines the frames of which weigh hundreds of tons. It should be apparent that in such cases it is for practical reasons completely impossible to apply the method now accounted for. Accordingly, in such cases it has been necessary to use the second method which involves that the very heavy machine frame is manufactured in several separate pieces which are transported to the place of installation where they are assembled to a frame whereupon the wire girdle is mounted. For obvious reasons it is impossible to deliver the girdle with the wires thereof pre-stressed to any significant extent. Instead, the wires have to be biased subsequently and, more particularly, not until the bobbin has been mounted around the frame which can absorb the inwardly directed forces generated by the pre-stressed wires. For

the sake of completeness it should, however, be added here that in the application of the second method the wires are actually given a certain small initial bias which is done in order to safeguard that all the layers of the winding are completely stretched already from the outset so that, when the biasing force proper is later on applied, the pre-stress will be substantially the same in all the individual turns of the winding.

The significance of the first-mentioned biasing method can be described in the following way. A machine frame, the different parts of which are either rigidly interconnected or do, at any rate, occupy constant relative positions, is, during the winding process, in consequence of the tensional force in the wire subjected to a successively increased compression. The second method involves that the machine frame, surrounded by the completed and, in principle, unbiased winding, is expanded so that the corresponding deformation of the bobbin results in a stretching of the wires and hence in the generation of a biasing force. The prior art way of causing that expansion was as follows. Let it be assumed that the frame comprises two horizontal yokes spaced by a number of columns. At least one of the yokes is mounted with preserved freedom of movement relatively to the remainder of the frame and then caused to move a small distance away therefrom resulting in an increase of the net circumference of the bobbin which stretching in turn pre-stresses the wires carried by the bobbin. The only realistic possibility of effecting that displacement of the yoke has been considered to consist in relying on the operational equipment of the machine. Accordingly, assuming that the machine is a hydraulic press, the hydraulic cylinder thereof has been utilized. lt was, however, explained above that the biasing force should exceed the reactional forces generated in the operation of the machine. For that reason it has been necessary to equip the machine with a hydraulic cylinder which during that preparation of the machine is capable of developing a higher force than the force it will later on be called upon to deliver the actual operation of the machine. Stated in other words this means that it has been necessary to overdimension the hydraulic system for the sole purpose of making it capable of performing this one time job. Other disadvantages of the method are that when the expansion of the frame is completed there still remains a difficult precision work, namely to fix the heavy portions of the frame in their new relative locations and subsequently to mount the spacing means necessary to maintain them in those positions. Moreover, if the operation of the machine reveals that the pre-stressing had actually not assumed the desired value, a further adjustment is required amounting to a repetition of the difficult adjustment work.

The main object of the invention is generally to facilitate the biasing of a prepared wire winding mounted on a machine frame.

Another object of the invention is to make it possible to bias the winding without relying on the hydraulic cylinder of the machine.

A further object of the invention is to provide simple and cheap means for carrying out the biasing operation.

A still further object of the invention is to make it possible directly to set the biasing at the required value and, if necessary, subsequently in a simple and quick way to readjust the biasing.

SUMMARY OF THE INVENTION A machine frame designed in accordance with the characteristics of the invention comprises forcegenerating means acting between the frame of the machine and the girdle which surrounds it and which supports the wires to be pre-stressed. The invention will below be explained in greater detail with reference to the accompanying drawing but it should be inserted here that the term wire has been used throughout this specification because the biasing elements are generally of circular cross-section. It is, however, evident that the cross-sectional shape of those elements is'not concerned with the present invention. Consequently, it is equally applicable also when the biasing elements of the girdle are constituted by tapes or have some other profile.

BRIEF DESCRIPTION OF THE DRAWINGS For purposes of illustration one embodiment of the invention is shown on the drawing as applied to a hydraulic gap press.

FIG. 1 is a perspective view of the press.

FIGS. 2 and 3 correspond to each other and do both show a transverse vertical view. While FIG. 2 illustrates the wire girdle before assembly of the bias-generating means, FIG. 3 refers to the assembled state of the frame and is a section taken along the line III-III in FIG. 1.

FIG. 3a is a vector diagram graphically illustrating up-stepping of the applied expansion forces.

FIG. 4 is a section taken along line IV-IV in FIG. 3.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENT The press illustrated in the drawing has a frame carried by a conventional base consisting of two feet 1 and 2. The frame comprises a lower yoke 3 and an upper yoke 4. The two yokes are spaced by two vertical columns 5 and 6. Column 5 interconnects two opposite yoke ends whereas column 6 is located centrally between the ends of each of the yokes. At the other ends of the yokes there are no columns. Instead, those yoke ends carry the tools of the gap press which are constituted by a die 7 and a piston 8. The latter is mounted for reciprocating movement in a double-acting hydraulic cylinder 9. Reference numerals l0 and 11 designate the pipe connections for the hydraulic fluid. The machine frame is, at the central column 6, surrounded by a wire girdle 12 which occupies a transverse position relatively to the frame. The girdle consists of a wire holder, or bobbin, 13 of channel-shaped cross-section which houses several wire layers 14. However, for ease of illustration the girdle shown in FIG. 4 is assumed to comprise only three layers of heavy wires 14. The wires consist of a special steel alloy exhibiting high tensile strength. Between on the one hand the plane bottom and top surfaces of yokes 3 and 4 and, on the other, the bottom and top inner wall portions of the oval girdle 12 there are located crescentshaped spacers 15 and 16 see particularly FIGS. 2 and 3.

The frame so far described belongs to the prior art. However, according to the invention there are between the central column 6 and each of the lateral inner walls of bobbin 13 mounted means permitting pre-stressing of wires 14. As has been explained above, the prestressing is achieved by expansion of the girdle after is has, in a substantially unbiased condition, been mounted around the machine frame. In accordance with the embodiment of the inventionhere illustrated the expansion means are constituted by two pairs of wedges 17, 18 and 19, 20 which are located at opposite sides of column 6 in the spaces between the column and the inner wall of bobbin 13. FIG. 4 does clearly illustrate the operation of the wedges but it should be mentioned that in order to illustrate the corresponding point the active angles of the wedges have been greatly exaggerated.

In this connection it should be strongly emphasized that the use of wedges corresponds to a preferred embodiment of the invention only and that the generic inventive idea is based on the realization that it is possible, without altering the relative positions of the various frame components, the yokes and the columns, to achieve the desired pre-stressing of the wires by subjecting the girdle to a force acting perpendicularly to the winding direction of the wires and applied near and parallel to the minor axis of the approximately elliptic or oval girdle. While it is very well feasible to let the expansion means act solely against the inner wall of the bobbin the corresponding structural problem are very much simplified if, as shown on the drawing, a portion of the machine frame, in this case the central column 6, is utilized as a part of the force-transmitting mechanism.

A comparison of FIGS. 2 and 3 indicates that, subsequent to the assembly and actuation of wedges 17-20, the bobbin has been deformed in the sense that its minor axis has been extended. After that extension the lateral walls of the bobbin are no longer vertical but form a small angle with the vertical plane. Also for the purpose of illustration the corresponding angle has been exaggerated as are the wedge angles in FIG. 4. In practice the deviation from the vertical plane amounts to about 510. In FIG. 3a there is shown a parallelogram of forces in which component A corresponds to the transverse force applied to the bobbin, component C to the reactional force absorbed by column 6 and vector B to the resulting force which accordingly is representative of the pre-stressing of wires 14. It is obviously possible to look upon B/A as a gear ratio. In the practical application of the invention that gear ratio could be around 5. This force-multiplication is accordingly attained thanks to the selection of the action points of the forces close to the minor axis as was above explained. According to the preferred embodiment the expansion forces are generated by means of wedges which results in a further reduction of the magnitude of the force necessary, eg by a factor of 10. Consequently, in the assumed case the final result is that a certain tightening force applied to the wedges results in a tensional force in wires 14 which is aboutSO times higher. Since the necessary total pre-stress'can be very high, e.g. of the order of 30,000 tons, it is realized that the invention yields a most valuable solution of the problem of creating such a pre-stress.

One of the additional advantages characterising the invention has already been referred to above, viz. the eliminated need of over-dimensioning the hydraulic system of the press as well as the need of, for the purpose of generating the pre-stress, first to displace a portion of the machine frame and then to fix it in its new position. The corresponding difference could be defined in the following way. According to the prior art the wires are biased by expansion of the machine frame proper which necessarily calls for repositioning of at least one portion of the frame. in contrast thereto, according to the present invention there is no need to displace any portion of the frame. Instead, the necessary expansion of the wire girdle is achieved by subjecting it to forces acting between the girdle and the frame. This means that the different parts of the frame can be permanently joined, as by welding. before the prestressing operation is initiated. A second advantage is that one has easy access to the places where the wedges or the corresponding expansion means are mounted for which reason that work can be carried out in a simple way and at low costs. Further, the increased rigidity of the frame guarantees an even and uniform contact pressure between the different parts of the frame and, to the extent it will be necessary to readjust the wire tension, such an operation can easily be carried out. For various reasons it is in practice often preferred to avoid permanent interconnection of the heavy frame parts meaning that they are held together solely by the biased girdle. in machine frames of that type application of the invention results in the further advantage that it is no longer necessary provisionally to support the frame portions during the pre-stressing stage. The need for such a support in the application of the known method has two grounds. One is that during the prestressing operation the frame columns are no longer securely clamped between the yokes. The second ground is that they are liable to get laterally displaced or even tilted when the shims corresponding to the expansion of the frame are to be introduced into the slots formed between the columns and the yokes.

While the wedge angles are selected so small that a self-braking action arises it is in the practical working of the invention still preferred to fix the wedges in their adjusted positions. There are mainly two reasons behind that procedure, namely safety aspects and a desire to secure a bias which is stable and uniform. Such a fixation can, however, be carried out by use of very simple means, such as conventional lock pins inserted in through holes in the wedges.

The above description of the operation of the arrangement is at the same time a description of the method according to the invention. It, therefore, only remains to be said that in the working of the invention it is possible in several respects to deviate from the procedure directly apparent from the embodiment here illustrated. This is especially true as far as the shape of the girdle and the design and operation of the expansion means are concerned.

What is claimed is:

l. A method of making a machine frame, particularly for heavy presses, comprising the steps of:

fabricating a frame member,

surrounding said frame member with a girdle com- 6 prising bias elements, and installing girdle expansion means between said frame member and said girdle for generating forces acting between said frame member and said girdle so as to expand said girdle in its circumferential direction, thereby tension-biasing said bias elements to thereby apply compressional forces to said frame member. 2. A machine frame, particularly for heavy presses, comprising:

a frame member, a girdle including bias elements surrounding said frame member for applying compressional forces to said frame member to counteract outwardly directed reactional forces to which said frame member is exposed in the operation of the machine. and

girdle expansion means mounted between said girdle and said frame member for expanding said girdle subsequent to said girdle being mounted on said frame member, the biasing of said bias elements being generated by expansion of said girdle under the influence of said girdle expansion means.

3. A machine frame as claimed in claim 2 wherein said girdle, in its unbiased condition, is of substantially oval shape, and said girdle expansion means is located near the minor axis of the oval.

4. A machine frame as claimed in claim 2 wherein said frame member includes a column member. and said girdle expansion means acts between said girdle and said column.

5. A machine frame as claimed in claim 4 wherein said girdle expansion means comprises wedge means mounted between said girdle and said column.

6. A machine frame as claimed in claim 5 wherein said wedge means comprises wedge members mounted on respective opposite sides of said column and engaging respective portions of said girdle.

7. A machine frame according to claim 2 wherein said girdle comprises a plurality of wires adjacent each other and surrounding said frame member, said wires comprising said bias elements.

8. A machine frame, particularly for heavy presses, comprising:

a frame member,

a girdle including bias elements surrounding said frame member for applying compressional forces to said frame member to counteract outwardly directed reactional forces to which said frame member is exposed in the operation of the machine, and wedge means mounted between said frame member and said girdle for expanding said girdle. thereby causing said bias elements to generate a biasing force.

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1. A method of making a machine frame, particularly for heavy presses, comprising the steps of: fabricating a frame member, surrounding said frame member with a girdle comprising bias elements, and installing girdle expansion means between said frame member and said girdle for generating forces acting between said frame member and said girdle so as to expand said girdle in its circumferential direction, thereby tension-biasing said bias elements to thereby apply compressional forces to said frame member.
 2. A machine frame, particularly for heavy presses, comprising: a frame member, a girdle including bias elements surrounding said frame member for applying compressional forces to said frame member to counteract outwardly directed reactional forces to which said frame member is exposed in the operation of the machine, and girdle expansion means mounted between said girdle and said frame member for expanding said girdle subsequent to said girdle being mounted on said frame member, the biasing of said bias elements being generated by expansion of said girdle under the influence of said girdle expansion means.
 3. A machine frame as claimed in claim 2 wherein said girdle, in its unbiased condition, is of substantially oval shape, and said girdle expansion means is located near the minor axis of the oval.
 4. A machine frame as claimed in claim 2 wherein said frame member includes a column member, and said girdle expansion means acts between said girdle and said column.
 5. A machine frame as claimed in claim 4 wherein said girdle expansion means comprises wedge means mounted between said girdle and said column.
 6. A machine frame as claimed in claim 5 wherein said wedge means comprises wedge members mounted on respective opposite sides of said column and engaging respective portions of said girdle.
 7. A machine frame according to claim 2 wherein said girdle comprises a plurality of wires adjacent each other and surrounding said frame member, said wires comprising said bias elements.
 8. A machine frame, particularly for heavy presses, comprising: a frame member, a girdle including bias elements surrounding said frame member for applying compressional forces to said frame member to counteract outwardly directed reactional forces to which said frame member is exposed in the operation of the machine, and wedge means mounted between said frame member and said girdle for expanding said girdle, thereby causing said bias elements to generate a biasing force. 